Washbasins, such as sinks, bathtubs, showers, and the like are typically made out of cast iron with a porcelain coating. With age, the porcelain chips, cracks, or is abraded away to present a rough surface which attracts dirt and, is difficult to clean, is unsightly, and unasanitary. Further, the porcelain will change color with age or may pick up stains. These worn and damaged surfaces are not only unsightly, but are more difficult to clean than smooth, new surfaces. The debris lodged in these damaged surfaces can present a health hazard, especially in situations where a number of people use the same washbasins.
Washbasins such as bathtubs, are typically located in bathrooms or restrooms having very restricted space and access. Kitchen sinks often are built into cabinets and tiled into place, so that removal of the sink destroys the tile. Further, many of the washbasins, especially bathtubs, are very heavy and bulky, further complicating any attempt at replacement. Thus, it is often impractical to entirely remove the washbasin for replacement, or even refinishing of the surface.
As a result of this restricted access and immobility, several methods have been developed to refinish the surfaces of these washbasins. One such method applies a filler material to smooth out the washbasin surface, followed by a coating of paint or a reapplication of porcelain to the surface. Unfortunately, such treatments often provide only temporary results with resurfacing being again required within a few years. Further, a considerable amount of time may be required for the filler material to properly set, and more time for the surface coat, or paint, to dry. The washbasin is unuseable during this time.
Several prior art U.S. patents describe various methods for putting a pre-formed plastic liner over an existing washbasin surface. For example, U.S. Pat. No. 4,158,585 to Wright, discloses a method for forming a plug from a bathtub, using that plug to form a master mold, forming a liner from the master mold, and then adhering the liner to the bathtub. However, the Wright process requires a considerable amount of time as well as multiple and complex steps in order to resurface the washbasin. Further, the formation of the liner envisions the use of factory equipment to form a master mold from the plug, and to draw the vacuum to form the liner.
The factory molding of such liners is usually required. For bathtubs, the large area and deep draw requires a large vacuum requiring factory equipment. For sinks, the area is smaller, but a deep draw is still required, and the shape is often complex, as in double kitchen sinks. Again, high vacuum capacity equipment is required. Draw molding of liners is also possible, but the high press forces still mandate a factory environment and safety precautions.
The use of such factory equipment inherently requires delays in transporting goods between the home and the factory, thereby increasing transportation costs. Still further, the factory vacuum equipment used to form the liner requires a very bulky and large capacity vacuum pump, which is costly, heavy, and generally immovable. The radiant heaters used to melt the plastic are typically very high amperage heaters requiring expensive and bulky electrical installations and power sources, as well as multiple safety code inspections and approvals. If a high power electrical source is not available, a sufficiently large generator can sometimes be temporarily obtained, however, such generators cost several hundred dollars a day to rent, are as large as a truck, have power cables as thick as your wrist (for the high power), and are generally impractical for use in a home environment.
There is such a variety in the styles, sizes, and shapes of washbasins that the plug and master mold as used in Wright, will typically not be usable on another washbasin. To the extent there are some repeated sizes and styles of washbasins, it is prohibitive from a cost and space viewpoint to inventory all of the master molds for the washbasins.
Additionally, the use of preformed liners, or liners formed through an intermediate plug and mold process, never exactly fit the actual washbasin onto which they are installed. Thus, there is typically a gap between the replacement liner and the original washbasin surface. If sufficiently large, mold can form in this gap. Adhesives are often required to be injected into this gap in order to fill the gap and restrain the slippage between the liner and the washbasin. These adhesives can take a considerable amount of time to dry or set. During this time, the washbasin is often unusable.
There is thus a need for a washbasin liner which can be installed quickly, to reduce the time in which the washbasin is not usable. Further, it is desirable to have the liner formed to the exact shape of the washbasin itself, rather than being formed on an intermediate mold, or a different washbasin, each of which may be of slightly different size or shape. Ideally, the liner would be formed on the washbasin in situ.
The prior art devices all envision factory molding devices involved heavy and bulky clamping fixtures and required large forces, because the molds were heavy and bulky, because the vacuum equipment was very large, bulky, and requires large pumps, and because the heaters operated at extremely high temperature, and required very high electrical currents.
In short, the prior art devices and methods required the space, safety, and permanent fixtures suitable only for industrial environments. There is presently no known, or appropriate way to mold a washbasin liner with the washbasin still in the bathroom environment. The unwieldly fixtures, the high forces, the dangerous operating voltages, and the high temperatures of commercial devices, are so unworkable in a bathroom environment as to make the mere idea of in situ molding appear not only unworkable, but ludicrous. Laughter was the initial response to initial inquiries on implementing this idea, from sources familiar with plastic molding.
If the idea of in situ liner molding seemed unbelievably funny, implementing that idea was not. Draw molding was attempted, but the draw mold cooled the pliable liner unless the mold was heated, thus giving a poor draw. Heating the mold seemed impractical. The fixtures to support the forces was unwieldly. The molding forces soon reached the point where the bathroom walls and floor were in danger of breaking during molding.
Vacuum molding was tried, but the edges of the liner deformed. A lip over one edge restrained that edge, but the typical bathtub is enclosed on three sides so as to preclude restraining lips on those sides. A clamping fixture was tried, but again, the required clamp force threatened to punch out the walls and the floor.
The "portable" vacuum pump lacked sufficient suction to mold the liner before it hardened. A larger pump became non-portable. Connecting the vacuum pump to the washbasin was awkward for sinks, since the drains were often accessible. However, that connection was not typically available for bathtubs since access holes to the drains are typically not provided. Tearing up the flooring was destructive and time consuming.
There was not enough space in the bathroom to heat the liner first, then place it on the washbasin and mold it, so the liner had to be heated in place. Unfortunately, it is hard to heat plastic from one side--it bows up to contact the heaters. Moving the heaters far enough away to avoid the bowed liner reduces the heater efficiency, and subjects the bathroom walls to potentially damaging temperatures. Slow heating of the liner at very low temperatures was tried, but the plastic can be over baked, making it unsuitable to mold.
Powering the resistive heaters appeared impossibly unportable. The high power required by the heaters far exceeded what was available, or safely usable in a bathroom--a dripping faucet could be fatal. A "portable" generator was tried, but it not only required a truck to move it, but the electrical cords were too heavy to readily move: copper conductor the size of your wrist is very heavy.
Fastening the liner to the washbasin required a vacuum seal, that could not only survive the molding temperatures, but could accommodate the thermal expansion of the liner as it heated. Hand adhesives cracked and broke. The colder, immovable washbasin not only exacerbated the thermal expansion problems, but limited the possible adhesive materials which could be used with the typically porcelain coated washbasins.
In short, attempts to implement the idea of in situ molding supported the prior view that such molding could not be done.